Method of expelling the liquid of cashew nut shells by heat



Patented Oct. 27, 1936 METHOD OF EXPELLING THE LIQUID OF CASHEW NUTSHELLS BY HEAT Edward R. Hughes, Morristown, N. .L, assignor to TheHarvel Corporation, a corporation of New Jersey No Drawing. ApplicationJuly 28, 1932,

' Serial No. 625,542

1 Claim. (01. 87-6) The present invention relates to methods and stepsfor the extraction 'of the liquid naturally occurring in the shells ofthe cashew nut (Anacardium orrientale), and the. invention also relatesto the liquid extracted by the methods of the present invention.

The cashew nut, and also the marking nut, has a shell comprising twowalls, one about the other and spaced apart from each other throughouttheir extent except at one small point where they come together andjoin. The space between these outer and inner walls is divided off byradial walls to define small cells which contain a liquid which in thecashew nut is generally rec- 15 ognized to be comprised of cardol andanacardic acid. Within the inner shell is the kernel which is highlyvalued for edible purposes and as a source of oil similar to olive oiland for use generally. About the kernel itself. is a paper like coveringsimilar to that found on the peanut or the almond. The outer and innershells are-tough and fairly hard but not brittle and thesecharacteristics together with the cushioning effect of the body ofliquid between the two shells make it diflicult to crack the shells andremove them.

from the kernel without breaking the latter. The dlfllculty in removingthis shell is further increased due to the fact that the shell liquidhas a vesicant action on the human skin.

3 The commercial method heretofore used for extracting the shell liquidand for freeing the kernels from the shell has been to char or burn theshells to such an extent that they canbe broken apart by hand. Thismethod has among others 35 the disadvantages of the adulteration of theshell liquid. with a great deal of carbon from the charred or burnedshells and the exposure. of the hands of the workmen to the vesicantaction of the shell liquid.

I have disclosed a method of extracting liquid from cashew nut shells inmy Patent No. 1,784,628, issued December 9, 1930, and inmy copendingapplication Serial No. 380,225, filed July 22, 1929 which latter is adivision of the application, of said patent, and of which this is acontinuation-in-part. Patent No. 1,777,808 to Thomas M. Rectorissued'October 7, 1930 also discloses a method for extracting oilfrom'cashew nut shells. The present invention is intended to provide amethod having advantages over methods heretofore used and to provide acashew nut shell liquid which can be secured uniformly in a high gradeand in a condition approximating the natural condition of the oil. Forexample, when the shells are heated to a point where they begin todarken and even below the actual charring the shell liquid is darkened,whereas by the present method the extent and time of heating can beregulated to secure shell liquid which is not darkened or is darkened toa minimum degree. 5

An object of the invention is to extract by explosion the liquid fromthe shell of the cashew nut, or of the marking nut, with the aid of heatto produce a pressure explosion of the shell liquid through the outershell wall and at the same time 0 to avoid darkening of the outside ofthe shell which might occur through excessive heating, the darkening ofthe shell being considered to darken the shell liquid upon contact.

Other objects and advantages of the invention will be apparent from thedescription of "the invention herein given.

According to the present invention I employ an organic liquid fortransmitting heat to cashew nuts or shells immersed therein, the organicliquid being selected so that the cashew nut shell liquid expelled bythe heat from the shells is not deleteriously affected thereby.

According to one method of the invention cashew nut shell liquid itselfis used, the liquid for starting the process preferably being secured byextraction with a solvent such as benzol with subsequent removal of thebenzol by evaporation, or by the process disclosed in my said Patent No.1,784,628 and copending application Serial No. 380,225. With thisparticular method there is the advantage that there is no necessity forseparating the cashew shell liquid of the heat transmitting bath.

'According to another form of the invention I use glycerine for the heattransmitting liquid, commercial glycerine of a good grade beingsuitable. The cashew nut shell liquid is of lower specific gravity thanthe glycerine and floats to the surface of the latter as it is expelledfrom the shells. The cashew nut shell liquid is skimmed off theglycerine and complete separation is done by passing through acentrifuge. Cashew nut shell liquid and glycerine will react at about475 F. but the, method of the present invention can be carried on wellbelow the reaction temperature of cashew nut shell liquid and glycerine.

In the practice of the present invention regard is taken of theabovementioned facts that heating for certain time and temperaturecombinations will darken the shell liquid. For some p poses it isdesired to get the shell liquid in as light a color as possible but forothers the lightest color is not necessary because subsequent treatmentof the shell liquid requires heating and 5 other treatment attemperatures that will darken it. Heating at certain temperatures andfor certain times also cooks the kernel and will darken it, excessiveheating of course causing excessive.

cooking and darkening of the kernels. Most roasters demand the kernelsin the uncooked or raw state and prefer to roast them themselves.Accordingly the temperatures and the time periods of heating areregulated or controlled to suit the desired needs or desiredcombinations thereof with respect to quantity of shell liquid expelled,color of the expelled shell liquid, and state of the kernel at the endof the process. For example, such heat treatment will be given as willexpel most or practically all of the shell liquid and the brownedkernels sold for what they will bring in that state; or the heating canbe regulated to secure maximum quantity of expelled shell liquidpossible while leaving the kernels in their natural color.

Another advantage of the process of the present invention is that theheating to expel the shell liquid from the shells changes the latterfrom their natural tough condition to a more brittle condition in whichthey are more readily removable from the kernels, and this step can beused for changing the shell from the tough to heating coils, or by meansof a second or outer bath, a double kettle, jacket or other suitablearrangement being used. And to get uniform distribution of heat theheating coils or double bath are favored. A heavy petroleum or Vaselineserve well for the outer bath when such is used. The temperature atwhich the process is carried out and the length of time during which thenuts or shells are subjected to the process temperature are regulated orcontrolled to secure best results with regard to darkening of the shellor shell liquid or darkening or cooking of the kernel and with regard tochanging the shell from its natural toughness to a more brittle state.

For some purposes the cashew nuts are soaked in water, for example, forsix to twenty-four hours and then dried, for example, from six totwenty-four hours or for several days at normal temperature say 68 F.,after which they are heated by being immersed in a bath of cashew nutshell liquid or other organic liquid, for example, glycerine. Thismoisture taken up by soaking helps raise a disrupting pressure on theshell when heated and also helps keep the kernels white, and the nutscan be immersed for a longer time at a given temperature without cookingthe kernels or blackening the shells and a greater proportion of theshell liquid expelled.

For removing a higlr percentage of the liquid from the shells of apractical sized batch of cashew nuts a temperaure in the neighborhood of325 F. is practical, with immersion in cashew nut shell liquid or inglycerine 'or other suitable organic liquid according to the method ofthe present invention, with a period of immersion of about four to eightminutes. With this treatment practically all of the shell liquid isexpelled, the shell is changed from the natural grey color to a yellowor light brown, and at seven or eight minute immersion the kernel hashardly or just about begun to cook. Yields of cashew nut shell liquid ofabout fifteen per cent of the total weight of the cashew nuts areconsistently obtained at a temperature of about 325 F. with immersionfor about four or five minutes. A temperature between about 300 F. and350 F. is a good working range for good shell liquid and good kernels,but I find that the cashew nut shell liquid can be expelled from theshell according to the method of the present invention in a temperaturerange extending from about 250 F. to about 450 F., the temperature useddepending on the requirements in the final products.

The immersing operation can be by hand, or

by semi-automatic or by automatic machinery as for example by themachinery illustrated and described in my said Patent No. 1,784,628 andcopending application Serial No. 380,225. The transmission of heat froma body of cashew nut shell liquid to the cashew nuts can be carried outby flowing a stream of heated cashew nut shell liquid over the cashewnuts. And the methods and steps of the present invention can be carriedon under vacuum to increase the pressure difierence between the outsideof the shell and the cellular spaces of the shell.

The treatment of cashew nuts according to the present invention makes iteasier to remove the shell from the kernel and if there is any residualliquid in the shell after treatment according to the present inventionsuch residual liquid can be removed by extraction with a solvent such asgasoline, ether and so on, or by pressing.

The cashew nut shell liquid obtained according to the method of thepresent invention is much lighter in color than commercial cashew nutshell liquid and is substantially entirely free of any outside materialsuch as dirt, carbon and moisture which are found in the commercialgrade. The iodine number is over 2'70, successive runs having been madewith an iodine number of about 275, with cashew nut shell liquidobtained by heating cashew nuts in a vacuum used as the first bath afterwhich the resulting mixture of cashew nut shell liquid was used.

Commercial cashew nut shell liquidcan be used as the heating bath tostart and this becomes gradually greatly diluted by thepurer cashew nutshell liquid as the number of batches increases and extra cashew nutshell liquid is removed from the bath. In such case the effect of thelower grade commercial cashew nut shell liquid becomes negligible.

In the claims the terms cashew nut and cashew nut shell liquid can beconsidered to mean also marking nut and marking nut shell liquid.

Having thus described my invention what I claim and wish to protect byLetters Patent is- In a method of expelling the liquid from the shell ofthe cashew nut with the aid of heat, the steps which comprise bringingthe nut in contact with moisture so that the nut-absorbs moisture andthen applying the heat by means of a body of cashew nut shell liquid incontact with the outside of the cashew nut, the temperature of the nutshell liquid body and the period of immersion being relatively adjustedto effect a discharge of a major portion of the contained shell liquidwithout scorching the nut shell kernels.

EDWARD R. HUGHES.

